Tip seal in a scroll fluid machine

ABSTRACT

A scroll fluid machine comprises an orbiting scroll and a fixed scroll. The orbiting scroll has an orbiting wrap and the fixed scroll has a fixed wrap. An engagement groove is formed at the end of the orbiting or fixed wrap. A tip seal engages in the engagement groove and comprises a PTFE sealing material on a sintered carbon backup material bonded with an adhesive made of epoxy resin.

BACKGROUND OF THE INVENTION

The present invention relates to a tip seal in a scroll fluid machine and especially to a tip seal engaged in grooves of the ends of orbiting and fixed wraps in a scroll fluid machine such as a scroll compressor or a scroll vacuum pump.

As disclosed in JP6-207588A and JP3248618B2, in a scroll fluid machine including a scroll compressor and a scroll vacuum pump, an orbiting scroll is rotatably mounted around an eccentric axial portion of a driving shaft via a bearing and comprises an orbiting end plate having an orbiting wrap. A fixed scroll comprises a fixed end plate having a fixed wrap. The fixed wrap engages with the orbiting wrap to form a sealed chamber between the fixed and orbiting wraps. A self-rotation-preventing device is provided to prevent the orbiting scroll from rotating on its own axis.

The orbiting scroll is eccentrically revolved with the eccentric axial portion of the driving shaft and the self-rotation-preventing device, so that the volume of the sealed chamber gradually decreases towards the center or increases towards the outer circumference.

The orbiting and fixed wraps comprise an involute curve in which diameter increases with rotation, a curve which comprises a plurality of short arcs having the same axis, or a combination thereof. A radial gap between the orbiting and fixed wraps is exactly determined so that the wraps do not contact each other or so that the gap is not too wide.

Engagement grooves are formed at the ends of the orbiting and fixed wraps and a tip seal engages in each of the engagement grooves so as to be in sliding contact with the facing end plate in a gas-sealing manner.

FIG. 4 is a perspective view of a fixed scroll 11 of the above documents. A tip seal 15 engages in an engagement groove 14 at the end of a spiral fixed wrap 13 of a fixed end plate 12 of a fixed scroll. An orbiting scroll (not shown) which engages with the fixed scroll and is driven by power is similar to the fixed scroll in structure of a tip seal.

As shown in FIG. 5, the tip seal 15 comprises a backup material 16 which makes air-tightness to the other end plate better. The backup material 16 is placed on the bottom of the engagement groove 14. A self-lubricating sealing material 17 is bonded on the backup material 16 with an adhesive 18.

The sealing material 17 is made of polytetrafluoroethylene under the trademark “Teflon” and abbreviated as “PTFE”.

The backup material 16 is made of heat-resistant elastic material in FIG. 3 of JP6-207588A, porous material such as polutetrafluoroethylene softer than the sealing material in JP3248618B2 or a band-shaped elastic tube made of heat-resistant rubber. The adhesive 18 is polyurethane.

If the scroll fluid machine as mentioned above is used under high radioactivity, the backup material 16 is deteriorated, broken and partially lost to make backup capability lost.

The polyurethane adhesive 18 is deteriorated to cause bonding force to be lost. The adhesive is crushed and powdered to go into each sliding portion thereby decreasing sealing capability or to leak to the outside thereby contaminating the environment.

The PTFE sealing material 17 is deteriorated by radioactivity, broken and partially lost to make it impossible to use.

To solve the problem in a tip seal in a scroll fluid machine used under high radioactivity, in FIG. 6, a sealing material 19 comprises polyimide resin and a backup material 20 comprises sintered carbon to constitute a tip seal 21.

It is actually impossible to bond the polyimide resin sealing material 19 to the sintered carbon backup material 20. Without bonding, the material 19 is merely placed on the backup material 20 in an engagement groove 14 at the end of a fixed wrap 13 and an orbiting wrap.

However, in the tip seal 21, polyimide resin for the sealing material 19 is very expensive to increase a total cost. The sealing material 19 and backup material 20 are not bonded. So it takes a lot of time to put the materials 19,20 in the groove 14. The sealing material 19 is lacking in flexibility and inconvenient in handling.

Such a tip seal used under high radioactivity is expensive and inconvenient in handling, but is widely used depending on its use.

But, in low radioactivity environment that need not the tip seal for high radioactivity, such an expensive tip seal for high radioactivity is actually used owing to no other choice.

It is obviously unreasonable and uneconomical, and it is necessary to provide a low-cost tip seal under low radioactivity.

SUMMARY OF THE INVENTION

In view of the disadvantage, it is an object of the invention to provide a tip seal in a scroll fluid machine, the tip seal being able to be used without being affected by low radioactivity, excellent in strength and physical properties and inexpensive compared with a known tip seal used under high radioactivity

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the invention will become more apparent from the following description with respect embodiments as shown in accompanying drawings wherein:

FIG. 1 is a vertical sectional view of an embodiment of a tip seal according to the present invention;

FIG. 2 is a vertical sectional view of another embodiment of a tip seal according to the present invention;

FIG. 3 is a perspective view of further embodiment of a tip seal according to the present invention;

FIG. 4 is a perspective view of fixed scroll;

FIG. 5 is a vertical sectional view of a known tip seal; and

FIG. 6 is a vertical sectional view of a known tip seal used under high radioactivity.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows the first embodiment of a tip seal in a scroll fluid machine of the present invention. The tip seal 3 engages in an engagement groove 2 at the end of a fixed or orbiting wrap 1 similar to that in FIGS. 4-6. The tip seal 3 comprises a backup material 4 made of sintered carbon and a sealing material 6 made of Teflon resin. The sealing material 6 is bonded on the backup material 4 with an adhesive 5 made of epoxy resin.

The backup material 4 and the adhesive 5 are hardly affected by low radioactivity of less than a certain limit. Even if the sealing material 6 should be cracked, broken or partially lost, separated ones will be unlikely to come into an operating portion of the scroll fluid machine.

FIGS. 2 and 3 show an improvement in adhesion of a sealing material to a backup material 4 with an adhesive 5.

In FIG. 2, opposite surfaces of the backup material 4 and sealing material 6 are formed uneven surface in which the adhesive 5 engages.

In FIG. 3, on opposite surfaces of the backup material 4 and the sealing material 5, a plurality of uneven lines are formed perpendicular to or inclined with respect to a longitudinal direction of the tip seal 3.

The uneven lines are not limited to straight lines, but may be curved or broken lines.

Thus, during operation, when different forces act to the backup material 4 and sealing material 6 in a longitudinal direction, the backup material 4 and sealing material 6 are effectively prevented from being separated from each other or moving relatively.

The foregoing merely relate to embodiments of the invention. Various changes and modifications may be made by a person skilled in the art without departing from the scope of claims wherein: 

1. A tip seal in a scroll fluid machine that comprises an orbiting scroll having an orbiting wrap and a fixed scroll having fixed wrap, ends of the orbiting and fixed wraps having an engagement groove in which the tip seal engages, said tip seal comprising: a backup material made of sintered carbon and disposed on a bottom of the engagement groove; and a sealing material made of polytetrafluoroethylene and disposed on the backup material to which the sealing material is bonded with an adhesive made of epoxy resin.
 2. A tip seal of claim 1 wherein one or both of opposite surfaces of the backup material and sealing material are uneven.
 3. A tip seal of claim 1 wherein one or both of opposite surfaces of the backup material and sealing material have a plurality of uneven lines which are not in parallel with a longitudinal direction of the tip seal. 